1. Field of the Invention
The present invention relates to a motor drive control device, and more particularly to a motor drive control device in which a motor is driven in accordance with a designation to raise and lower a raised/lowered member so that the raised/lowered member is raised and lowered.
2. Description of the Related Art
Conventionally, a motor drive control device is applied to, for example, a power window control device provided at the door of a vehicle. If the motor drive control device is applied to the power window control device in this way, a motor is used, and in accordance with the operations of a switch which designates raising and lowering of a door glass, the motor is driven so as to raise and lower the door glass. Further, in order to detect catching of a foreign object between the door glass and a window frame or the like, a pulse encoder, which synchronizes with the rotation of the motor and generates a pulse signal, is provided at the power window control device.
By calculating the amount of variation in the cycle of the pulse signal generated by the pulse encoder and by determining whether the calculated amount of variation is greater than a threshold value, a determination is made as to whether a foreign object has been caught between the door glass and the window frame. If it is determined that the foreign object has been caught therebetween, the motor is driven reversely (the door glass is lowered) by a certain amount and then stopped.
Incidentally, in order to be able to determine precisely whether the catching of a foreign object has occurred, it is assumed that a pulse signal synchronized with the rotation of the motor is generated by the pulse encoder. In the power window control device, it is not determined whether failure of the pulse encoder has occurred.
As a result, in a case in which the pulse encoder has failed and a pulse signal which is not synchronized with the rotation of the motor is generated, or in a case in which the pulse signal is not generated even if the motor rotates, a user cannot tell whether these cases are caused by the failure of the pulse encoder or by the catching of the foreign object.
Accordingly, even if the failure of the pulse encoder has occurred and a designation to raise the door glass is made, since it is not determined that the pulse encoder has failed, the operation of the door glass cannot be differentiated from the ordinary raising operation thereof.